Method for the cementation of steel.



No. 876,862. PATENTED JAN. 14, 1908.

A E. DAVIS. n METHOD EOE TEE EEMEETATION 0E STEEL.

APPLICATION FILED APR.10;1901.

Ill

vet

TinTTnn sTaTEs PATENT ermee.

CLELAND DAVIS, OF UNITED STATES NAVY, ASSIGNOR,v DY MESNE ASSIGNMENTS, TO CARNEGIE STEEL COMPANY, OF PIITTSBURG, PENNSYLVANIA, A CORPORATION NEW JERSEY.

' and useful'lmprovements in Methods for t e Cernentation of Steel; and I do hereby deelare the following to bea full, clear, and eX- act description of the invention, such as will enable ot ers skilled in the art to which 'it appertains to make and use the same.

, My' invention relates to an improved method for the cementation of steel, 'and it consists of certain novel features that will be hereinafter described and claimed. In processes 01"' this character the main objects to be attained are, first, to be able to regulate the depth of carbonization and of chill, so as to preserve the vmost eifective proportion between the hard Jface and the tough back; and second, at the same time preserve the integral character of the metal throughout.

If a plate be heated by an electric furnace to any desired depth to a Vmolten point, or to `one approaching fluidity, the back being kept comparatively cool, carbon can be introduced in the desired. quantity and will be absorbed instantly or in a very short time, uniformly throughout the molten portion and shade away into the body of the plate.

In all the processes of cementation hitherto employed, the shading oil' of carbon begins 'from the surface 'or immediately below it.

The accompanying drawings show an electric i'urnace adapted to carry out the 'foregoing process, and in which,

J Figure l represents a section through a lurnace constructed 'for carbomzing armor plate,

the section of thelcover being shown alo'ng.

the line 1,-1 of Fig.. 2, and Fig. 2 represents an inverted plan view of the detachable air tight cover to go over the side of the plate that is to be heated.

`A represents 'the masonry, preferably 'Firebrick, having the plate a, twyers a and asbestos and tire clay backing elet inside the same. Y

B represents the armorplate sup orted on eye-beams C, which are insulate as at c. The entire plate should-be insulated in this or any other convenient way.

represents a removable cover which may be removed as by means of the cable E Specification of Letters Patent.

Application filed April 10.1901. Serial No. 55,124.

,tric current is turned on.

METHOD FOR TPIE CEIEENTATION OF STEEL.

' Patented Jan. Al, 1908.

passing over the pulley F, or in any other convenient way. This cover makes an air tight joint over the side of the plate to be treated. The said cover is packed with asbestes, or fire clay, or similar material G, in which a plurality ci' electrodes H are held, and these electrodes are connected with the source of electricity by suitable conductors indicated diagrammaticall at l. rThe circuit to the source ot' electricity is completed by means of the contacts K and the conductors L. The contacts K may be placed at suitable points on the sides or bottom of the plate. A layer of powdered carbon M is interposed between` the cover D and the face of the plate to be heated. Air, either hot or cold, may be blown through the twyers a from any suitable air blast, not shown, 'and thus lower the temperature of the under side of the plate, while the upper side of the plate is being heated, or other means may be einployed to keep the back of the plate cool, if preferred.

ln practice, the plate isput in position, a

`measured quantity oi" powdered or granular carbon M is spread over the surface to be treated, the cover l) is lowered in place and the joints made tight, and the necessary elec- This speedily' raises the temperature of the carbon M and the upper part of the plate, until the latter reaches almost,l if not quite, the fusing point, and the layers of carbon will be absorbed into the plate. ln the meantime the lower part of the platemay be kept comparatively cool,A

by means of an air blast through the twyers a. lf the electric current be ke it on until all the carbon M has disappeared, t len it will be known that this has been carried into the body of the plate, and in this way a measured degree of carburization may be obtained. Moreover, by varying the current and the time of its ap lication, the carbon may be. carried throng into the late, causing the cementation to be deeper t anwi'ththe processes now in use.

A direct current would, I believe, be preferable to an alternating current, as the tendency of the carbon would' be to follow the current. lf desired, a single electrode might cover the entire mass oi carbon M, or a single carbnn electrode might be used, covering the entire face oi the plate to be tr ated, or the electrodes ll might be differently grouped,

y and the currents passed through them seriatim, or in groups, or the'pulverized carbon M might be done away with, and 'the carbon su plied direct from the carbon electrodes, al of which, and any other grouping or electrodes I intend to include within the scope of niy claims.

Instead ol having the circuit closed, I may establish an arc betweenthe electrodes and the face of the Cplate lto be treated, and I prefervthis metho Vfor carboni'zing; or I may so adjust the electrodes and the plate, as to give a suitable heatingl efl'ect.

No hard and fast rule can be laid down as to the treatment of any 'particular class of' lates, as the treatment would diil'er for diierent grades of steel, and for different sizes of plates, etc., but the electrical character' istics once being established, it is evident that conditions can be reproduced with great accura'cy by use of the volt meter and animeter, and by regulating the amount of carbon to be introduced ,into the late.'

In practice it may be foun that the quality o the metal can be iilnproved,after carbonizing, by treatment such' as forging, annealing, etc., the plate being removed from the furnace for this purpose.

It will be evident that this method' of treatment ma be used with any plate in which it is-desire to make harder or Ychill deeper on one side than on the other.

While I have l'described this invention as a plied to the treatment of armor plate for t e urpose of face hardening the same, it

.will e obvious that the same is applicable to I claim and desire to secure the cementation or hardening of steel plates wherever it is desiredto have one side or a plate harder than the other. 4 y y `Having thus described my invention, what of the United States, i'sh', I

l. The process 0i treating previously formed iron or steel plates which consists in heatingone face of the solidI plate vto an approximately molten conditionl by means a heavy current-of electricity, and car- 'burlzlng vsald molten face, substantially as described. y

formedI iron or steel plates which consists in heating one face of the solid late to approximately molten condition li a heavy current of electricity, and carburizing said molten faceand in maintaining y Letters Patent y means of.

the opposite face of said plate at a lower '.temperature, substantially as described.

.of the plate from air, heating the carbon covered face to' an approximately molten condition by a heavy current of electriclty,

erv

and maintaining the opposite portion of said j plate at a lower temperature; substantially as described. 4

5. The method of treatingriion or steel plates, consisting in applying carbon to one face of the plate, screeningsuch face from the air, and thenl applying an electric current to such face to raise it to an approximately molten conditioii substantially as described.

6. The method of .treating iron or steel plates, consisting in applying solid powdered carbon to .one face of a solidined plate,-cover ing and protecting such portion of the plate from the air, heating the carbon-covered race to approximately a molten condition by a heavy current of electricity, and simultaneously applying cooling means to the other portion of said plate to keep it at a lower temperature; substantially as described.

7, The herein described method which consists in impregnating a face of a metal Y.

plate with carbon to a prescribed kdepth while said depth of the plate is ina molten condition, the remaining portion of the late being in a solidV condition, substantial yas described.

s. The .herein described method which consists in-remelting one face of a metal plate to a prescribed depth. while-maintaiibV mg the remaining portion of the plate in a comparatively solid condition anduniormly impregnating the melted portion with car, 1 I bon, substantially as described. 2, The process of treating previously In testimony-whereof, I aiiix my signature in presence of two witnesses." 4CLELAND DAVIS.

Witnesses:

GRAFTON L. McGILL,

' FRED ENeLnRT. L 

